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Betaine

Trimethylglycine

Well toleratedHumectanthumectantskin conditioninganti-irritant

No meaningful concern for most people; irritation is possible but rare.

Also written as: Trimethylglycine · Glycine Betaine · TMG

What it is

Betaine is an amino acid derivative obtained mainly from sugar beet molasses, a by-product of sugar refining. Living cells, including skin cells, use it as an osmolyte, a compound that lets them hold onto water without disrupting their internal chemistry. In cosmetics it acts as a light humectant that hydrates without the tackiness of glycerin, and it is often added to soften the feel of cleansers.

What it does well

  • Hydrates the skin and supports its own water-handling machinery

    A 2024 clinical study found that trimethylglycine, especially combined with aloe vera extract, upregulated aquaporin-3 (the water-channel protein in skin cells) and improved measured hydration both immediately and over 28 days.

    Moderate evidence

  • Reduces the harshness of cleansing formulas

    Betaine is routinely added to surfactant systems to lower irritation potential. This is well established in formulation practice, though most of the supporting data comes from manufacturer and industry testing rather than independent trials.

    Moderate evidence

  • Light, non-sticky texture

    Betaine gives a hydrating effect without the tacky after-feel of high-glycerin formulas, which is why it often appears alongside glycerin rather than instead of it.

    Strong evidence

Worth knowing

  • No meaningful safety concerns identified

    Betaine is a normal dietary and cellular compound, is not a recognised sensitiser, and has no EU restriction. Reported reactions in cosmetic use are essentially absent.

    Matters most toNo specific group.

Where the EU stands

No specific restriction

Permitted in EU cosmetics with no concentration limit. It is not listed in the banned, restricted or preservative annexes of the Cosmetics Regulation.

Sources (1)

Every link goes to the original: a journal, a PubMed record or an EU document.

  1. [1]
    Synergetic Effects of Aloe Vera Extract with Trimethylglycine for Targeted Aquaporin 3 Regulation and Long-Term Skin Hydration

    Molecules · 2024 · doi:10.3390/molecules29071540

    Trimethylglycine (betaine) increased aquaporin-3 expression and, in a clinical test, safely improved skin hydration both after a single use and over 28 days.

Masks that contain Betaine